+. −. =∆. 1. 3. 1. 1. /. /. 10/. ,. EN 1993-1-2 calculation of protected steel
temperature. EN 13481-4 calculation of fire protection material thermal
conductivity ...
Intumescent Coating Performance under Different Fire Conditions Yong Wang & Jifeng Yuan, University of Manchester
1
Background
Performance based fire engineering design is more widely taken up Intumescent coating 50% market share Intumescent coating performance is fire dependent Assessment of intumescent coating based on standard fire tests sufficient? If not, what is the alternative?
2
Current Assessment Method: BS 13481-4 EN 1993-1-2 calculation of protected steel temperature
∆Ts =
(T (d
f
− Ts )Ap / V
1 ) λ ρ / C p p ,t a a 1 + φ 3
(
)
∆t − eφ / 10 − 1 ∆θt
EN 13481-4 calculation of fire protection material thermal conductivity
V 1 φ /10 λ p ,t (t ) = d p × × ca ρ a × (1 + φ / 3) × × ∆Ts + (e − 1)∆θt Ap (T f − Ts )∆t
3
Fire Tests
Under standard fire exposure Under two types of parametric fire curves
4
Standard Fire Tests
5
Parametric Fire Tests 1200
Slow Fire Fast Fire
Fire Temperature (C )
1000
800
600
400
200
0 0
15
30
45
60
75
90
Time (min)
6
Basis of Parametric Fires
Room is 5 x 5 m2, and 3m high. Normal weight concrete wall with thermal conductivity λ=1.6W/mK, density ρ=2300kg/m3, and specific heat C=980J/kgK. Window size: 1.68m wide and 1.2m high
Number of Windows
Corresponding Opening factor (m-1/2)
Fire load (kg [wood]/ m2 floor area)
Test 1
1
0.02
30
Test 2
4
0.08
100
7
Test set-up Sample 1: 254mmX254mm Sample 2
Sample 1
Flange 25.3mm Web
15.6mm
DFT 0.569mm in fast fire 0.615mm in slow fire Sample 2: 203mmX203mm Flange 12.5mm Web
8.0mm
DFT 0.839mm in fast fire 0.834mm in slow fire
8
After the Tests Slow fire test
Fast fire test
9
Thermal Conductivity
Effective Thermal Conductivity 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0
200
400
600
800
Temperature
10
Confirmation of Back Analysis 1000 900 Temperature (C)
800 700 600 500 400 300 200 100 0 0
1000
2000
3000
4000
Time (s)
11
Prediction of Parametric Fire Tests: using effective thermal conductivity (green) and new method (black) Temperature (C)
254 Flange 800 700 600 500 400 300 200 100 0 0
1000
2000
3000
4000
5000
6000
Time (s)
Slow Fire 12
Prediction Results continued Temperature(C)
254 Web 800 700 600 500 400 300 200 100 0 0
1000
2000
3000
4000
5000
6000
Time(s)
Slow Fire
13
Prediction Results continued Temperature(C)
203 Flange 800 700 600 500 400 300 200 100 0 0
1000
2000
3000
4000
5000
6000
Time(s)
Slow Fire
14
Prediction Results continued Temperature(C)
203 Web 800 700 600 500 400 300 200 100 0 0
1000
2000
3000
4000
5000
6000
Time(s)
Slow Fire
15
Prediction Results continued 254 Flange
Temperature(C)
1200 1000 800 600 400 200 0 0
1000
2000
3000
4000
5000
6000
Time (s)
Fast Fire
16
Prediction Results continued Temperature (C)
254 Web 1200 1000 800 600 400 200 0 0
1000
2000
3000
4000
5000
6000
Time (s)
Fast Fire
17
Prediction Results continued Temperature (C)
203 Flange 1200 1000 800 600 400 200 0 0
1000
2000
3000
4000
5000
6000
Time (s)
Fast Fire
18
Prediction Results continued Temperature (C)
203 Web 1200 1000 800 600 400 200 0 0
1000
2000
3000
4000
5000
6000
Time (s)
Fast Fire
19
Summary
It is not appropriate to extrapolate effective thermal conductivity values obtained under the standard fire condition to parametric fire conditions New method provides much better results
20
Basis of New Method
Define chemical reactions and associated mass loss Reaction rate constant (Arrhenius Equation): K j = Aj exp( −
∂m j
Mass loss rate:
∂t
= m j K j f (α ) α :
Ej ℜT
), j = 1, 2,3
Degree of conversion
Key Chemicals :1. :1. Inorganic acid sources, 2. Blowing agent 3. Charring material
Determine expansion process Expansion rate: ∂x
∂t
=
1 ∂m2 ρ g ∂t
( x ≤ Emax x0 )
Emax: Final expansion ratio
Thermal conductivity of porous material with changing porosity Coating = Solid phase + Gas phase (Gas phase conductivity 8 λ rad = deσ T 3 Radiation part: λ = λ d: Bubble size 3 +λ g
cond
)
rad
Heat of decomposition, required in the chemical reaction Convection heat loss from gas transport
21
Hypothesis The aforementioned parameters are intrinsic properties of an intumescent coating. Therefore, they are applicable to different fire conditions. These properties can be determined by independent means that are not fire dependent.
22
Kinetic Values by Thermogravimetric Analysis (TGA) 120 100 80
Mass 60 40
fraction 20 0 0
200
400
600
800
1000
A1
300
A2
2000000
A3
5
E1
54000
E2
110000
E3
60000
Y1
28
Y2
17
Y3
55
Vc
0.65
Temperature
23
Bubble Size: Slow Fire
24
Bubble Size: Fast Fire
25
Expansion Coefficients -
Slow Fire Large section: Web=44, Flange=36 Small section: Web=50, Flange=39 Fast Fire Large section: Web=44, Flange=31 Small section: Web=48, Flange=44
26
Method to Determine Expansion
Temperature to start expansion Temperature to complete expansion Time between these two temperatures Expansion factor related to time duration Emax
Tc T2 T1
t1
t2
Time
t2-t1
27
Summary - 1
Current method of assessment not applicable to different fire conditions The proposed method provides a feasible alternative Main material input data: chemical kinetics, bubble size, maximum expansion rate Kinetics constants to be obtained from TGA. They can be assumed to be constants for an intumescent coating product. Bubble size can be measured from small scale tests. It can be assumed to be a constant for an intumescent coating product.
28
Summary - 2
Expansion rate requires further study. A method has been outlined. A new EPSRC funded project will start in the new year to find a method to determine expansion rate and to perform comprehensive validation of the new method for different products and different fire conditions. Future: different intumescent coating products for different “realistic (parametric)” fires?
29
Acknowledgements
30
